1. Field of the Invention
The present invention relates to an encoder signal processing circuit that processes signals from a plurality of encoder heads.
2. Description of the Related Art
An encoder is configured to generate analog periodic signals (encoder signal) of at least two mutually different phases in accordance with displacement of a movable body. Generally, an encoder includes a scale mounted on a fixed body and an encoder head provided on a movable body arranged opposite to the scale to output an encoder signal accompanying changes in relative position with respect to the scale. Such an encoder processes an encoder signal output from the encoder head by an encoder signal processing circuit. Accordingly, the traveling direction, position, displacement, speed and the like of a movable body can be measured.
In recent years, encoder signal processing circuits configured to process encoder signals from a plurality of encoder heads by a single encoder signal processing circuit is proposed by, for example, Jpn. Pat. Appln. KOKAI Publication No. 7-139967.
The encoder signal processing circuit proposed by Jpn. Pat. Appln. KOKAI Publication No. 7-139967 is configured to successively input encoder signals from a plurality of encoder heads into the encoder signal processing circuit to acquire all encoder signals from respective encoder heads in the same sample holding period so that the encoder signals from the respective encoder heads are detected within the periods which are considered the same periods. In this case, if the number of encoder heads increases, the time needed to complete processing on all encoder signals increases correspondingly. Therefore, to process a plurality of encoder signals in a short time by using the configuration of Jpn. Pat. Appln. KOKAI Publication No. 7-139967, ICs and the like used as an encoder signal processing circuit need to be capable of faster processing in accordance with an increase in the number of encoder heads.
The present invention is made in view of the above circumstances and an object thereof is to provide an encoder signal processing circuit capable of efficiently processing encoder signals output from a plurality of encoder heads by a single processing circuit.